1. Technical Field
The present invention relates to an image processing device, an image display device, and a method of controlling an image processing device.
2. Related Art
In the past, there has been known a display device for performing double speed display. In JP-A-2011-39256 (Document 1), there is disclosed a display device, which performs double speed processing on image data to generate double-speed processed image data, then compresses (encodes) the double-speed processed image data to generate compressed image data, and then transfers the compressed image data to a driver in the case in which the driver for driving a display panel performs the double speed display. Further, the driver of the display device expands (decodes) the compressed image data to decompress the double-speed processed image data, and then drives the display panel in response to the decompressed double-speed processed image data. According to such a display device as described above, the amount of data transferred in the display device is reduced to thereby make it possible to reduce the necessity of high-speed data transfer.
However, in the display device described in Document 1, in the case of performing the double speed processing, it is necessary to compress the image data to transfer the image data to the driver, and then expand the image data by the driver to drive the display panel. As described above, since the image data is compressed (encoded) in the format requiring the expansion (decode), it is difficult to perform image processing with the data in the compressed state. For example, in the case of performing the image processing such as a keystone distortion correction, there is required a processing circuit for expanding (decoding) the compressed data before inputting the compressed data to the image processing circuit.
In recent years, there has been known an image processing device provided with a plurality of image processing circuits such as a circuit for the double speed display, a circuit for the keystone distortion correction, and a circuit for noise reduction. In such an image processing device as described above, there has been known a device, which writes the image data into a frame memory incorporated in the image processing circuit to perform the image processing without compressing (encoding) and expanding (decoding) the image data. However, if the image data is once written into the frame memory, there occurs an image delay time (a frame delay) as much as one frame. When performing such image processing a plurality of times, the delay time corresponding to the image processing occurs. When the frame delay occurs, there is a problem that a delay occurs when the image output from the image display device follows the operation of the controller by the user in the case in which the image display device displays the image such as a video game requiring real-time processing as an important factor. In the case in which the frame delay is large, the nature of the game is spoiled in the case in which the operation of the user fails to be reflected on the display despite the operation of the user due to the delay of the image processing.
Further, although it is possible to shorten the image delay time (the frame delay) by speeding up writing/reading of the image data into the frame memory of the image processing circuit, in order for speeding up the writing/reading, a measure such as increase in the clock rate or expansion of the bus width becomes necessary. In this case, speeding up of the devices or expansion of the wiring area is required, and there is a problem that the manufacturing cost rises.